Though I want to say that not every single movie or drama could be used as an ideal English learning material, <em>Stranger Things</em> is indeed amazing to watch. If you wish to aim for nice pronunciations from this drama, I personally think that the character of Joyce (Winona Ryder) has a great speaking tone, very clear, vivid rhythm!
Other highly popular TV series such as <em>Friends</em> (all 10 seasons) is certainly a good choice. Or, if you also prefer British English accent, I’d also recommend <em>Downton Abbey. </em>
Hope my answer helps. Best of luck!